This application is a continuation of U.S. appilication Ser. No. 10/231,663, filed Aug. 29, 2002, now abandoned, which was the National Stage Application of International Application No. PCT/AU01/01665, filed Dec. 21, 2001, which claims priority from Australia Application No. PR2231, filed Dec. 21, 2000.
The present invention relates to coupling systems for securing pipes. More particularly, the invention relates to a coupling device for polymeric pipes, wherein a pipe is inserted into the coupling device to a first position and wherein tightening of the coupling device causes the pipe to be drawn further into the coupling device.
Polymeric pipe couplings are well known and typically include a body, nut, and grip ring. A pipe is inserted into the body. Tightening of the nut compresses the grip ring that in turn engages the pipe. Further tightening of the nut causes urging of the pipe further into the body. A typical coupling is described and illustrated in our U.S. Pat. No. 5,593,186 entitled xe2x80x9cCoupling for Outer Surface Engagement of Polymeric Pipexe2x80x9d. The described coupling is adapted for engagement with the outer surface of a polymeric pipe. The coupling includes a sub-assembly of a compression sleeve, a resilient gasket ring permanently attached to the inner end of the compression sleeve, a gripping member and a nut. The gasket ring encounters an abutment in a socket in the body as the nut is tightened, and further tightening of the nut radially compresses the grip ring member so that its inwardly directed barbed projections engage the outer surface of a pipe to which the coupling is attached. The end of the pipe is freely insertable through the gripping member and sleeve and into the socket in the body. There are also provided abutment surfaces within the body coupling and the nut that abut inner and outer surfaces of a flange outstanding from the outer end of the compression sleeve. Also disclosed is an embodiment with a transition spigot having a barbed tail inserted into an end of a pipe enabling the coupling to accommodate a range of similar but different diameter pipes.
The coupling described in the aforesaid specification and other earlier couplings have proven to be very successful, both technically and commercially. Failure is almost unknown and in some areas of the world fittings made in accordance with that specification have achieved great success.
A practical problem which is frequently encountered with couplings made in accordance with said U.S. Pat. No. 5,593,186 (and other fittings having in common a gripping member and a tightening nut), is that when the nut has been partially tightened it radially compresses the gripping member causing the inwardly directed barbed projections to engage the outer surface of a pipe to which the coupling is attached. Further tightening of the nut then results in the pipe being urged in the direction of the nut travel along its longitudinal axis due to the force exerted on the pipe by the barbed projections. But, because the pipe is typically inserted into the coupling until its end abuts against an abutment surface, there is no additional room for the pipe to move into. As the nut is further tightened, the pipe is subject to significant forces that result in its deformation and leads to changes in the flow of the fluid through the pipe. Further, the rotation of the nut requires more and more torque to effect the appropriate compression on the seal, and at times, it may be incorrectly assumed that the nut is fully tightened due to the resistive forces of pipe leading to couplings that leak.
It is therefore an object of the present invention to provide for a coupling whereby when the pipe is inserted into the coupling it is caused to be held at a first location, and whereby when the coupling nut is further tightened the pipe is caused to be drawn further towards a second location.
It is a further object of the present invention to provide for a coupling that allows manual insertion of the pipe and that prevents the pipe from being inserted too far into the coupling.
There is currently no prior art known to the applicant whereby a pipe is caused to abut a coupling at a first location and whereby further tightening of the coupling nut will cause the pipe to be drawn towards a second location.
In accordance with the above objects and those that will be mentioned and will become apparent below, the coupling device in accordance with this invention comprises a body having an external thread and annular inner surfaces defining a socket within the body of larger outer diameter at an outer end than at an intermediate location of said socket; a stop extending at least partially around the annular inner surface in the intermediate location of said socket at a position offset from the end of said intermediate location where the end is distal from said outer end; a nut
In preference, the projections are wedge shaped projections whose longitudinal direction extends in the longitudinal direction of the coupling. Preferably, the front surface of the wedge facing the outer end is disposed at an angle other than a right angle but greater than 45 degrees to the longitudinal axis. In a preferred embodiment, the front surface has at least two faces whose angle to the longitudinal axis is less than 90 degrees. having an internal thread at an inner end thereof engaging said body external thread, an inwardly facing abutment surface between ends of said nut, and an outwardly converging internal circular surface between said abutment surface and an outer end of said nut; an annular sleeve having an abutment surface at is outer end co-operable with said nut abutment surface, and a resilient gasket secured to its inner end; a deformable gripping member having an outwardly converging outer surface complementary to said outwardly converging internal nut surface, the gripping member having an internal surface with barbs extending radially inwardly therefrom; internal diameters of said socket inner end, sleeve and gripping member all being slightly greater than an external diameter of a pipe to which said coupling is securable, such that an end of said pipe is freely insertable through said gripping member and into said socket intermediate part until it abuts the stop, and tightening of said nut over said external thread causes axial movement of said gasket ring, sealable engagement of said gasket ring and said body, radially inward deformation of said gripping member such that the said barbs clamp said pipe, and axial movement of said pipe over the stop and towards the end of said intermediate location.
The use of the stop assists in properly coupling the pipe. A user inserts the pipe into the coupling to a location where they can feel resistance to the pipe moving further into the coupling. This position then still provides the pipe with room to move inwardly into the pipe as it does when the nut is tightened. In this way, since the pipe is not inserted too deeply into the coupling its end is not caused to deform under tightening of the nut.
In one embodiment of the invention, the stop is an annular abutment surface extending circumferentially around the annular inner surface. Preferably, the stop is a plurality of projections positioned circumferentially and symmetrically around the inner annular surface.
In preference there are at least three projections disposed 120 degrees angularly to each other. Preferably the height of the projections is at least equal to the thickness of the pipe.
Advantageously, the projections are wedge shaped projections whose longitudinal direction extends generally perpendicular to the longitudinal direction of the coupling.
Advantageously, the wedge shaped projections are of an arcuate shape.
In a further embodiment of the invention, the pipe coupling is of the type where a pipe is freely insertable into the coupling and includes a body having annular inner surfaces and external threads; a nut having internal threads adapted to engage said body; a grip ring disposed within the body and of a shape and configuration that rotation of the nut causes it to move in both the axial and longitudinal direction, said nut having projections adapted to engage said pipe when the nut is tightened and having an end adapted to engage a gasket and move it into a sealing cavity when the nut is tightened, wherein said body includes an abutment surface located at a position away form the ends of said body to provide a guide to the user when inserting the pipe freely into the coupling and where the abutment surface is of a shape and configuration such that under rotation of the nut the pipe is caused to move over said abutment surface and further into said coupling.
Thus, the present invention provides for an improved pipe coupling where there is a mechanism to indicate to a user that a pipe has been sufficiently inserted into the coupling whilst there still remaining room for the pipe to move axially inwardly into the coupling as it does under the forcing of the grip ring.
The typical coupling to which the present invention can be applied includes a gripping member and a sub-assembly of a compression sleeve and resilient gasket ring generally attached to the inner end of the compression sleeve. A pipe end is freely insertable through the sub-assembly and into a socket in the body of the coupling abutting against a pipe abutment surface or stop. The gasket ring encounters an abutment in its socket in the body as the nut is tightened, wherein tightening of the nut radially compresses the gripping member so that its inwardly directed barbed projections engage the outer surface of a pipe to which the coupling is attached. When the barbs have engaged the pipe, further tightening of the nut causes the pipe to be forced inwardly into the coupling past the pipe abutment surface and towards an abutment shoulder. The longitudinal distance between the pipe abutment surface and the abutment shoulder is generally equal to or greater than the longitudinal travel of the nut from the position at which the barbed projections have gripped the pipe to the final tightened position of the nut. There are also provided abutment surfaces within the body of the coupling or the end of the body, and the nut, that abut inner and outer surfaces of a flange outstanding from the outer end of the compression sleeve.